Overview - This Program Project explores the idea that when a cell enters the meiotic state, it undergoes a radical re-wiring of gene expression programs. A more conservative view was that meiotic cells are broadly similar to vegetative cells, but express additional, meiosis-specific genes. We explore a more radical view in which even genes that are expressed in both vegetative and meiotic cells are expressed in a different fashion, regulated by different transcription factors in meiotic cells. Furthermore meiotic cells may use a larger repertoire of mechanisms to control gene expression than vegetative cells. In short, when cells differentiate from the vegetative state into the meiotic state, their gene expression programs are extensively re-wired. We will study this re-wiring, and novel, meiosis-specific regulatory mechanisms. The first three projects use S. cerevisiae, and focus on regulatory mechanisms in early, middle, and late meiosis, respectively. The fourth project uses S. pombe, and focuses on novel meiotic regulatory mechanisms. Projects. 1. Wiring of Gene Expression in the Early Meiotic Program (Dr. Futcher) 2. Meiotic Cdc7 switches and substrates, and the activation of Ndt80 (Dr. Hollingsworth) 3. Histone modification and Chromatin Switches in the Meiotic state (Drs. Neiman and Sternglanz) 4. Novel mechanisms of gene regulation in Meiosis: Antisense RNAs and RNA processing. (Dr. Leatherwood) The research Projects will be supported by a Microarray Core Facility, which will play a crucial role in all four projects.